An I/O connector, such as a USB receptacle and the like, is provided in a side face of a casing of most of laptop computers in the prior art, so as to facilitate user operation. And the laptop computers have various sizes to meet different use requirements. As the I/O connector is generally provided on a circuit board and partially protrudes from an edge of the circuit board to be received in a corresponding opening of the side face of the casing, the edge of the circuit board is required to be close to the side face of the casing as much as possible. In other words, a size of the circuit board is required to match with a size of the casing, so as to allow the periphery edge of the circuit board close to the side face of the casing. Therefore, the laptop computer having different sizes respectively requires circuit board having corresponding sizes, and the circuit boards having the same size can not be used. That is, when the laptop computers having different sizes are developed, the circuit boards having the corresponding sizes are additionally required and developed, thereby resulting in long development time and high cost.
In order to solve the above problem, Taiwanese patent No.TWI361024B1 provides a motherboard which can be mounted on laptop computers having different sizes. The motherboard comprises a first portion, a second portion and a connecting device movably connected to the first portion and the second portion, the connecting device can adjust a relative distance between the first portion and the second portion, so as to adjust an overall size of the motherboard. The first portion and the second portion are respectively provided with connectors, and a cable which has connectors at both ends respectively is used for connecting the connectors positioned in the first portion and the second portion, so as to electrically connect the first portion and the second portion.
However, a total of one cable and the four connectors are additionally required for connecting the first portion and the second portion, causing high manufacturing cost. In addition, signal transmission between the first portion and the second portion must flow through two pairs of connectors and one cable and increasing the number of connection tends to increase insertion loss and tends to cause poor electrical characteristics.